Tea is a natural source of GABA, but special production techniques can increase the levels of natural GABA. The Japanese discovered that if tea is fermented in a nitrogen-rich atmosphere the levels of GABA increase 5 to 10 times.
Due to the popularity of GABA tea in Japan, the Japanese government has set standards for the production of GABA tea. According to these standards, GABA tea must have at least 150 mg of GABA per 100 grams of tea.
GABA tea is produced in stainless steel vacuum drums. The oxygen is removed and replaced by a molecular inert gas such as nitrogen. Nitrogen is often used to preserve food since bacteria and fungi cannot exist in a nitrogen atmosphere. This property of nitrogen led to the discovery of GABA tea when Japanese scientists were experimenting with food preservation methods in the 1980's.
Fresh tea leaves are placed in the vacuum container where they are kept in the nitrogen-rich atmosphere for a period of 6 to 10 hours. They must also be heated above 40 degrees Celsuis and have a pH enviroment of 5.8. All these factors combined produce tea with the greatest levels of GABA.
Why does this work?
The mechanism of GABA tea production has been the subject of much scientific study. Because of the health benefits of GABA tea, Japanese scientists have investigated the process behind GABA tea production.
Several factors are involved in producing tea with high GABA concentrations. Tea which naturally has the highest levels of GABA are high grade teas, and the most GABA is found in the stems followed by the top leaf and then by the two lower leaves. For this reason, the stem should be included when picking tea meant for GABA production.
Tea which is shaded for 10 - 15 days before picking will also have higher concentrations of GABA. This increases the levels of glutamic acid in the tea, and it is glutamic acid which eventually is converted into GABA.